Apoptosis is a program of cellular suicide initiated by a wide range of physiological stimuli. While an array of clearly defined changes in cellular morphology accompany apoptosis, the underlying biochemical events which produce cell death are poorly understood. Dr. Kornbluth proposes to use frog (Xenopus) egg extracts to study the signaling pathways which contribute to the regulation of apoptosis. Xenopus eggs contain a vast storehouse of components sufficient to produce 4000 embryonic cells without any growth or input from gene transcription. Therefore, they are a rich source of material which can be used for in vitro reconstitution of cellular processes in a manner which is difficult or impossible in other systems. Using such an in vitro reconstituted, Dr. Kornbluth previously found that the phosphotyrosine-binding adapter protein, crk, is absolutely required for the induction of apoptosis in vitro. to further investigate the apoptotic process in the egg extract, Dr. Kornbluth proposes two specific aims. These are 1) to evaluate the potential role of known-crk-interacting proteins in apoptotic signaling and 2) to identify novel crk-interacting proteins and determine whether they function in apoptotic pathways.